When grain (particularly corn) is harvested it has a higher moisture content than desired or necessary for safe storage. The presence of too much moisture will cause the grain to become heated and therefore spoil during storage. Accordingly, harvested grain which contains too much moisture to permit simple bin storage must be dried (i.e., reduced in moisture content) to prevent spoilage.
The most common and accepted techniques for drying grain have involved forcing heated air through the grain to absorb the excess moisture. Normally the air is heated by means of propane or natural gas burners, although it may also be heated electrically. This, of course, requires a very large amount of fuel to heat the volume of air necessary to dry grain in large bins. Furthermore, the heated air must be forced through the grain thoroughly in order to dry the gain in all parts of the bin. This requires the use of one or more large fans of high capacity. Operating such fans also consumes much energy.
A common design for the type of bin utilizing the forced air drying system involves the use of a perforated floor through which the heated air is forced upwardly. Thus, moisture in the grain near the floor must be driven upwardly through grain above it, thereby making the grain wetter as the moisture moves upwardly. This creates a moisture front or bank that must be driven through all of the grain in the bin. This often limits the rate at which the bin may be filled because accumulation of too much moisture will cause spoilage of the grain.
Although various types of bins have been proposed which permit some air ventilation, none of these structures are suitable for storage of high moisture grain (such as shelled corn). For example, U.S. Pat. No. 1,817,270 describes a grain bin including a tubular air conducting stack. Hinged to the stack at each of two separate vertical positions are four arms or auxiliary ventilator members spaced 90.degree. from each other around the stack. This bin structure, however, does not provide for entry of outside air into the bin nor does it provide sufficient ventilation to prevent spoilage of grains with high moisture content. The portable grain storage tank described in U.S. Pat. No. 2,357,705 has essentially the same disadvantages, although it does allow for air to enter the bottom of the stack. A variation of this type of bin structure is described in U.S. Pat. No. 1,977,389, but it does not cure the basic deficiencies described above.
Another type of bin structure is described in U.S. Pat. No. 2,645,991 including a horizontal air duct extending through the bin and a number of vertical ducts extending through the bin and a number of vertical ducts extending upward from the horizontal duct. Fans at the outer ends of the horizontal duct force air into the system. However, there is insufficient air movement in the bin structure to enable high moisture grain to be kept therein without spoilage.
Slightly different apparatus is described in U.S. Pat. No. 2,737,878 including networks of ventilating pipes arranged horizontally at predetermined levels within the storage structure. Compressed air is then forced through the horizontal tubes. In still another variation, described in U.S. Pat. No. 2,126,107, there are intersecting vertical and horizontal tubes within the structure.
Another variation is described in U.S. Pat. No. 3,357,110 in which several (e.g., eight) tubes are vertically disposed within a cylindrical bin. The bin has an inverted cone bottom. A centrally located elevator lifts grain from the bottom of the bin to the top. The grain is then discharged onto a cone-shaped upper floor which enables the grain to slide off in all directions and downwardly within the bin. This structure, of course, requires movement of the grain in the bin.
In U.S. Pat. No. 3,913,469 there is described yet another type of grain bin structure in which a plurality of vertical dividers separate the bin into a plurality of vertically extending grain cells. Each divider is defined by a pair of vertical air permeable side walls to provide a vertical air space between grain cells.
None of the structures previously described provide the advantages and efficiencies provided by the storage structure of the present invention.